An initially parallel cylindrical beam travels in a medium of refractive index `mu(I)=mu_0+mu_2I`, where `mu_0` and `mu_2` are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius.
30 . At the beam enters the medium, it will

Options

A. diverge
B. converge
C. diverge near the axis and converge near the periphery
D. travel as a cylindrical beam

Answer

B

Explanation

In the medium, the refractive index will decrease from the axis towards the periphery of the beam.
Therefore, the beam will move as one move from the axis to the priphery and hence the beam will converge.